Such an interesting and convoluted topic. We are people and we all have our preferences for what ever reason.
On this planet, our race is unique because of the variety of people we have. Think about it, you have elephants...you know what a elephant generally looks like, for the most part they are the same - even in other parts of the world. Humans on the other hand come in all shapes, sizes, colors, etc. Some people only like blonde hair and blue eyes, some green eyes, dark skin, and others don't give a damn about your exterior (for the most part), but your interior. Personally this is where I fall.
While granted we all want the "most handsome, muscled, and gosh darn big "penis'd" (lol)" guy out there, the first thing you see is "the skin", the surface. If the surface doesnt match what you "do" in general, then you may miss out on someone who meets all of the criteria of what you want in a man, except that he is darker or lighter skinned. Unfortunate.
From my short time on this earth, I have dated a variety of guys each with his own quirks, personality, and complexion. For a lot of them I was the first "darker" skinned person they had EVER done anything with (for the record I am mixed - af. amer, irish, nat. american) and it came down to them seeing past the skin/surface and more about my merit as an individual, cause, well...i'm pretty awesome. Yes, people have not gone out with me because of my skin tone - but I do not have ill will against those people because it probably would not have worked out anyway. He didn't take the time to truly get to wholly know who I am so why bother taking the time to know you?
In any case, if more people thought my way then we would be a society of elephants. All the same. Its good to have variances and differences, I think. It keeps us true to who we are. (sorry for the term paper)